Increased growth in brain volume compared to typically developing infants during the first year of life has been shown to accurately predict whether a child at high-risk of developing autism spectrum disorder is likely to receive a diagnosis of the disorder at age two, according to a small neuroimaging study published online this week in Nature. Further research, including replication in larger sample sizes, is needed before this plausible brain biomarker can be developed into a potential clinical tool to inform early detection in high-risk populations.
Enlarged brain volume has previously been observed in children with autism, but the development of these changes and their relation to the behavioural symptoms of the disorder remain unclear.
Heather Hazlett and colleagues conducted a prospective study of 106 infants who had an older sibling with a clinical autism diagnosis (high-risk) and 42 infants with no immediate family history of autism (low-risk). Analysing neuroimaging data obtained between 6 and 24 months of age, the authors find an increased growth rate of cortical surface area in the high-risk infants that were later diagnosed with autism compared to the low-risk infants and high-risk infants not diagnosed later with autism in the first year of life. Increased surface-area growth was linked to the total brain overgrowth observed in the high-risk infants’ second year of life. They also find that these changes in brain volume are associated with the social deficits that emerge in the second year. Finally, the authors employ a machine-learning algorithm that can predict, with good accuracy, which children in the high-risk group would eventually be diagnosed with autism at 24 months of age.
The authors note that it remains unknown whether these brain changes are specific to autism or might overlap with other neurodevelopmental disorders.